startupcache/StartupCache.h

   1 /* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef StartupCache_h_
   7 #define StartupCache_h_
   8
   9 #include "nsClassHashtable.h"
  10 #include "nsComponentManagerUtils.h"
  11 #include "nsZipArchive.h"
  12 #include "nsIStartupCache.h"
  13 #include "nsITimer.h"
  14 #include "nsIMemoryReporter.h"
  15 #include "nsIObserverService.h"
  16 #include "nsIObserver.h"
  17 #include "nsIOutputStream.h"
  18 #include "nsIFile.h"
  19 #include "mozilla/Attributes.h"
  20 #include "mozilla/MemoryReporting.h"
  21 #include "mozilla/StaticPtr.h"
  22
  23 /**
  24  * The StartupCache is a persistent cache of simple key-value pairs,
  25  * where the keys are null-terminated c-strings and the values are
  26  * arbitrary data, passed as a (char*, size) tuple.
  27  *
  28  * Clients should use the GetSingleton() static method to access the cache. It
  29  * will be available from the end of XPCOM init (NS_InitXPCOM3 in nsXPComInit.cpp),
  30  * until XPCOM shutdown begins. The GetSingleton() method will return null if the cache
  31  * is unavailable. The cache is only provided for libxul builds --
  32  * it will fail to link in non-libxul builds. The XPCOM interface is provided
  33  * only to allow compiled-code tests; clients should avoid using it.
  34  *
  35  * The API provided is very simple: GetBuffer() returns a buffer that was previously
  36  * stored in the cache (if any), and PutBuffer() inserts a buffer into the cache.
  37  * GetBuffer returns a new buffer, and the caller must take ownership of it.
  38  * PutBuffer will assert if the client attempts to insert a buffer with the same name as
  39  * an existing entry. The cache makes a copy of the passed-in buffer, so client
  40  * retains ownership.
  41  *
  42  * InvalidateCache() may be called if a client suspects data corruption
  43  * or wishes to invalidate for any other reason. This will remove all existing cache data.
  44  * Additionally, the static method IgnoreDiskCache() can be called if it is
  45  * believed that the on-disk cache file is itself corrupt. This call implicitly
  46  * calls InvalidateCache (if the singleton has been initialized) to ensure any
  47  * data already read from disk is discarded. The cache will not load data from
  48  * the disk file until a successful write occurs.
  49  *
  50  * Finally, getDebugObjectOutputStream() allows debug code to wrap an objectstream
  51  * with a debug objectstream, to check for multiply-referenced objects. These will
  52  * generally fail to deserialize correctly, unless they are stateless singletons or the
  53  * client maintains their own object data map for deserialization.
  54  *
  55  * Writes before the final-ui-startup notification are placed in an intermediate
  56  * cache in memory, then written out to disk at a later time, to get writes off the
  57  * startup path. In any case, clients should not rely on being able to GetBuffer()
  58  * data that is written to the cache, since it may not have been written to disk or
  59  * another client may have invalidated the cache. In other words, it should be used as
  60  * a cache only, and not a reliable persistent store.
  61  *
  62  * Some utility functions are provided in StartupCacheUtils. These functions wrap the
  63  * buffers into object streams, which may be useful for serializing objects. Note
  64  * the above caution about multiply-referenced objects, though -- the streams are just
  65  * as 'dumb' as the underlying buffers about multiply-referenced objects. They just
  66  * provide some convenience in writing out data.
  67  */
  68
  69 namespace mozilla {
  70
  71 namespace scache {
  72
  73 struct CacheEntry
  74 {
  75   nsAutoArrayPtr<char> data;
  76   uint32_t size;
  77
  78   CacheEntry() : data(nullptr), size(0) { }
  79
  80   // Takes possession of buf
  81   CacheEntry(char* buf, uint32_t len) : data(buf), size(len) { }
  82
  83   ~CacheEntry()
  84   {
  85   }
  86
  87   size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) {
  88     return mallocSizeOf(data);
  89   }
  90 };
  91
  92 // We don't want to refcount StartupCache, and ObserverService wants to
  93 // refcount its listeners, so we'll let it refcount this instead.
  94 class StartupCacheListener MOZ_FINAL : public nsIObserver
  95 {
  96   ~StartupCacheListener() {}
  97   NS_DECL_THREADSAFE_ISUPPORTS
  98   NS_DECL_NSIOBSERVER
  99 };
 100
 101 class StartupCache : public nsIMemoryReporter
 102 {
 103
 104 friend class StartupCacheListener;
 105 friend class StartupCacheWrapper;
 106
 107 public:
 108   NS_DECL_THREADSAFE_ISUPPORTS
 109   NS_DECL_NSIMEMORYREPORTER
 110
 111   // StartupCache methods. See above comments for a more detailed description.
 112
 113   // Returns a buffer that was previously stored, caller takes ownership.
 114   nsresult GetBuffer(const char* id, char** outbuf, uint32_t* length);
 115
 116   // Stores a buffer. Caller keeps ownership, we make a copy.
 117   nsresult PutBuffer(const char* id, const char* inbuf, uint32_t length);
 118
 119   // Removes the cache file.
 120   void InvalidateCache();
 121
 122   // Signal that data should not be loaded from the cache file
 123   static void IgnoreDiskCache();
 124
 125   // In DEBUG builds, returns a stream that will attempt to check for
 126   // and disallow multiple writes of the same object.
 127   nsresult GetDebugObjectOutputStream(nsIObjectOutputStream* aStream,
 128                                       nsIObjectOutputStream** outStream);
 129
 130   nsresult RecordAgesAlways();
 131
 132   static StartupCache* GetSingleton();
 133   static void DeleteSingleton();
 134
 135   // This measures all the heap memory used by the StartupCache, i.e. it
 136   // excludes the mapping.
 137   size_t HeapSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf);
 138
 139   size_t SizeOfMapping();
 140
 141 private:
 142   StartupCache();
 143   virtual ~StartupCache();
 144
 145   enum TelemetrifyAge {
 146     IGNORE_AGE = 0,
 147     RECORD_AGE = 1
 148   };
 149   static enum TelemetrifyAge gPostFlushAgeAction;
 150
 151   nsresult LoadArchive(enum TelemetrifyAge flag);
 152   nsresult Init();
 153   void WriteToDisk();
 154   nsresult ResetStartupWriteTimer();
 155   void WaitOnWriteThread();
 156
 157   static nsresult InitSingleton();
 158   static void WriteTimeout(nsITimer *aTimer, void *aClosure);
 159   static void ThreadedWrite(void *aClosure);
 160
 161   static size_t SizeOfEntryExcludingThis(const nsACString& key,
 162                                          const nsAutoPtr<CacheEntry>& data,
 163                                          mozilla::MallocSizeOf mallocSizeOf,
 164                                          void *);
 165
 166   nsClassHashtable<nsCStringHashKey, CacheEntry> mTable;
 167   nsRefPtr<nsZipArchive> mArchive;
 168   nsCOMPtr<nsIFile> mFile;
 169
 170   nsCOMPtr<nsIObserverService> mObserverService;
 171   nsRefPtr<StartupCacheListener> mListener;
 172   nsCOMPtr<nsITimer> mTimer;
 173
 174   bool mStartupWriteInitiated;
 175
 176   static StaticRefPtr<StartupCache> gStartupCache;
 177   static bool gShutdownInitiated;
 178   static bool gIgnoreDiskCache;
 179   PRThread *mWriteThread;
 180 #ifdef DEBUG
 181   nsTHashtable<nsISupportsHashKey> mWriteObjectMap;
 182 #endif
 183 };
 184
 185 // This debug outputstream attempts to detect if clients are writing multiple
 186 // references to the same object. We only support that if that object
 187 // is a singleton.
 188 #ifdef DEBUG
 189 class StartupCacheDebugOutputStream MOZ_FINAL
 190   : public nsIObjectOutputStream
 191 {
 192   ~StartupCacheDebugOutputStream() {}
 193
 194   NS_DECL_ISUPPORTS
 195   NS_DECL_NSIOBJECTOUTPUTSTREAM
 196
 197   StartupCacheDebugOutputStream (nsIObjectOutputStream* binaryStream,
 198                                    nsTHashtable<nsISupportsHashKey>* objectMap)
 199   : mBinaryStream(binaryStream), mObjectMap(objectMap) { }
 200
 201   NS_FORWARD_SAFE_NSIBINARYOUTPUTSTREAM(mBinaryStream)
 202   NS_FORWARD_SAFE_NSIOUTPUTSTREAM(mBinaryStream)
 203
 204   bool CheckReferences(nsISupports* aObject);
 205
 206   nsCOMPtr<nsIObjectOutputStream> mBinaryStream;
 207   nsTHashtable<nsISupportsHashKey> *mObjectMap;
 208 };
 209 #endif // DEBUG
 210
 211 // XPCOM wrapper interface provided for tests only.
 212 #define NS_STARTUPCACHE_CID \
 213       {0xae4505a9, 0x87ab, 0x477c, \
 214       {0xb5, 0x77, 0xf9, 0x23, 0x57, 0xed, 0xa8, 0x84}}
 215 // contract id: "@mozilla.org/startupcache/cache;1"
 216
 217 class StartupCacheWrapper MOZ_FINAL
 218   : public nsIStartupCache
 219 {
 220   ~StartupCacheWrapper() {}
 221
 222   NS_DECL_THREADSAFE_ISUPPORTS
 223   NS_DECL_NSISTARTUPCACHE
 224
 225   static StartupCacheWrapper* GetSingleton();
 226   static StartupCacheWrapper *gStartupCacheWrapper;
 227 };
 228
 229 } // namespace scache
 230 } // namespace mozilla
 231 #endif //StartupCache_h_